TABLE 1. Bill of Materials that I used for assembling the
SunBot II project. You may substitute parts as necessary.
The VEX quadrature optical encoders are optional and will
be used in a future article to calibrate the stepper motor
commands to azimuth and elevation positions.

issues were probably caused by backlash from the gears
and also by not detecting the hard stops accurately using
the VEX limit switches.

Some of these problems could be corrected by
calibrating the movements, or by using a different stepper
motor drive mechanism other than gears. Timing belts and
direct drive are possible alternatives to fix this problem. In
addition, the VEX firmware needs more work to be able to
track the sun correctly, once the mechanical problems have
been ironed out.

Wrap-Up

Using simple VEX hardware with some PIC18 C
firmware, precise and repeatable movements are possible
for your next robotics or automation project, using the
information in this article. Stepper motors need not remain
a mystery to use if you build the SunBot II or similar
applications. The SunBot II robot demonstrates very
complicated micro-stepping used to aim a solar panel at the
sun using stepper motors.

In the next installment, I plan to show a PIC18 C
application that I actually used to move the solar panel, and
some issues that I encountered with it. I will also cover
using the quadrature optical encoders and limit switches,
and calibrating the stepper motors which you will need to
start tracking the sun with your own SunBot II.